This application claims the priority benefit of Taiwan application serial no. 91125123, filed Oct. 25, 2002.
1. Field of Invention
The present invention relates to an organic light emitting diode (OLED). More particularly, the present invention relates to a red light organic light emitting diode device and organic luminescent materials thereof
2. Description of Related Art
So far, lightweight displays with high efficiency, such as, liquid crystal displays, have been widely developed. However, quite a few problems still exist in liquid crystal displays, including narrow viewing angles, response time not short enough for high-speed animations and the need of back light modules resulting in more power consumption. In addition, it is difficult to manufacture large-scale panels for the liquid crystal displays.
Therefore, a new flat display technology is recently developed to solve the above problems, which is the organic light emitting diode (OLED) display. The organic light emitting diode is a display component, taking advantage of self-luminescent characteristics of its organic luminescent or fluorescent materials for display. The OLED mainly comprise a pair of electrodes and an organic electroluminescence (EL) layer. The organic EL layer includes luminescent materials. The holes and electrons from the transparent anode and the metal cathode can cause the luminescent materials to form exitons, thus resulting in light emission (electroluminescence).
As disclosed in Applied Physics Letters, Vol. 51, No. 12, pp. 913-15 (1987), C. W. Tang and S. A. VanSlyke reported a double layered organic light emitting diode, consisting of an organic EL layer and a hole transport layer or a electron transport layer, together with an electrode pair. As holes are injected from anode and electrons are injected from cathode, passing through the hole transportlayer or the electron transport layer, to the organic EL layer, the holes and electrons combine in the organic EL layer so as to generate electroluminescence. The luminescent material of the organic EL layer can generate luminescence with different chromaticity, depending on the energy differences (gaps) between the ground state and the excited state of the materials.
In the Japanese Journal of Applied Physics, Vol. 27, No. 2, pp. L269-L271 (1988) and Journal of Applied Physics, Vol. 65, No. 9, pp. 3610-16 (1989), a three-layered structure of the organic light emitting diode is reported. In addition to the electrode pair, the structure consists of an organic EL layer, a hole transport layer and a electron transport layer. From these reports, it is proved that development toward low driving voltage and high brightness is possible.
For full-color displays, it is essential to have colors of high purity. Because of using organic materials as luminescent materials, the color of the light (luminescence), the wavelengths of the red, green and blue light, can be modified by changing the design of the molecular structures.
However, there are some problems existing in the organic light emitting diodes, especially in developing red light luminescent materials with high stability and high efficiency. At present, for the red light luminescent materials, 4-(dicyanomethylene-6-(p-dimethylaminostyryl)-2-methyl-4H-pyran) (DCM) or its derivatives doped in tris(8-quinolinol)aluminum (AlQ3) are commonly used. However, these materials can not meet the requirements of brightness and purity for the full-color organic light emitting diode devices.
Accordingly, the present invention provides an organic light emitting diode (OLED) device and materials of its organic electroluminescence (EL) layer thereof, which fulfills the requirement for the full-color OLED display.
Accordingly, the present invention provides an OLED device and luminescent materials of the organic EL layer thereof, in order to offer an OLED device with high efficiency and red light luminescent materials with high color purity.
The present invention provides an OLED device and materials of the organic EL layer thereof. The OLED device comprises a first electrode disposed on a substrate, an organic EL layer disposed on the first electrode and a second electrode disposed on the organic EL layer. The luminescent material of the organic EL layer disclosed in the present invention is a compound modified from coumarin compounds, denoted as the following formula (1): 
wherein R1xcx9cR4 individually represents hydrogen, substituted or non-substituted alkyl group, substituted or non-substituted cycloalkyl group, substituted or non-substituted alkoxyl group, substituted or non-substituted alkenyl group, substituted or non-substituted amino group, substituted or non-substituted aryl group, heterocyclic group, aryloxy group, and substituted or non-substituted propenyloxy group. In addition, R3xcx9cR4 can be the fused ring formed from any two of the aforementioned groups. Z represents xe2x80x94OR5 or xe2x80x94NR6R7. X and Y individually represents oxygen atom, sulfur atom or xe2x80x94NR8. A is substituted or non-substituted polyterphenyl (including cyclohexenyl group as shown in the following formula (2) and naphthalenylidenyl group as shown in formula (3)). B and C are electron-pulling groups, either the same groups or different groups, such as, cyano group, indandione, benzoimidazole, benzooxazole or benzothiazole.
Specifically, R1xcx9cR4 individually represents hydrogen, substituted or non-substituted alkyl group with 1-10 carbon atoms, substituted or non-substituted cycloalkyl group with 1-10 carbon atoms, substituted or non-substituted alkoxyl group with 1-10 carbon atoms, substituted or non-substituted alkenyl group with 1-10 carbon atoms, substituted or non-substituted amino group, substituted or non-substituted aryl group with 6-30 carbon atoms, heterocyclic group with 6-30 carbon atoms, aryloxy group with 6-30 carbon atoms, and substituted or non-substituted propenyloxy group with 1-10 carbon atoms. R5xcx9cR8 individually represents hydrogen, substituted or non-substituted alkyl group with 1-10 carbon atoms, substituted or non-substituted cycloalkyl group with 1-10 carbon atoms, substituted or non-substituted alkenyl group with 1-10 carbon atoms, substituted or non-substituted aryl group with 6-30 carbon atoms, heterocyclic group with 6-30 carbon atoms, aryloxy group with 6-30 carbon atoms. R14xcx9cR19 individually represents hydrogen or alkyl group. 
B and C are independently electron-withdrawing groups, such as, dicyano group, cyano group, indandione, benzoimidazole, benzooxazole or benzothiazole, as shown in the following formulas (4)-(9). 
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.